1. Field of the Invention
The present invention relates to power supplies. More particularly, the present invention relates to a power supply for producing complex non-periodic waveforms from a sum of stored waveforms.
2. Description of the Related Art
Numerous industries utilize power supplies for various purposes. For certain applications, it is desirable to have a certain degree of control over the output of power supplies. For example, electrolytic plating requires power to be supplied to the electrodes in a manner so as to properly plate an object. Plating tends to build up around edges and sharp protrusions. The more irregularly shaped the object to be plated is, the more difficult it is to apply a uniform layer of metal.
Due to increasing complexity of objects requiring plating, particularly in the micro-electronics industry, the need for power supplies allowing for precise control over the signals produced has grown. Signals which produce pulses having varying positive and negative magnitudes are needed to gradually build up metal layers on surfaces, and to remove excess build-up in problematic areas are a necessity.
Prior devices which offer some degree of control in the electrolytic plating industry are limited in their flexibility and restrict the user to periodic pulsed signals. One such device is disclosed in U.S. Pat. No. 5,273,642 to Crites et al. Crites et al. disclose an apparatus for electroplating wafers in which a programmable controller is used to regulate a waveform. While such controllers are useful for relatively simple surfaces, they restrict the user to programming periodic waveforms, and do not enable the user a full range of control over the waveforms.
U.S. Pat. No. 4,517,059 to Loch et al., discloses a similar power supply device which provides a varying waveform for an electrolytic process. Forward and reverse pulses are provided by means of feedback and a pre-programmed microprocessor. U.S. Pat. No. 4,863,579 to Asaoka also discloses a power supply device for electrolytic plating in which various pulses are discharged as determined by a command center. These devices offer the user very limited control over the waveforms, and are thus insufficient for plating complex surfaces. Furthermore, when different types of waveforms are required to accomplish different tasks or separate stages of the plating process, such stages are not readily combined into one stage or process using the above devices.
Therefore, there is a need for a power supply device which can be easily controlled and programmed by the user to provide a full range of waveforms in order to optimize the resulting plating process.